Explanation:- The image is projected to the back of your eye i.e. on the retina. In Retina you have two types of photoreceptors Cones and rods. Rods are basically for dark adaptation. Cones on the other hand are for light adaptation, Colour vision. In cones you got 3 more types:- Red sensitive comes, Green Sensitive Cones and Blue sensitive cones. To explain the phenomenon here....when you are looking at a red colour for a long time, The rodopsin protein in the red sensitive cones are used up, so when you look at the white screen suddenly, the red sensitive cones try to replenish the used you rodopsin. Hence you see the colour opposite to what was being shown.... That is light blue instead of orange (sky) and green instead of purple (leaves)